The present invention relates to a method of and a device for magnetic-abrasive machining of parts.
Magnetic-abrasive machining of parts is generally known in the art. It is usually that cylindrical parts are machined in the following way. A magnetic field is generated, a part is placed in the magnetic field and rotated about its axis and simultaneously oscillated along its axis, and a magnetic-abrasive powder is introduced into the area of machining simultaneously with cooling liquid which is poured into the area. In the device for the magnetic-abrasive machining, electromagnetic inductors are used, in which the magnetic flux is closed through a metal magnetic conductor and pole shoes as well as working gaps and the part to be machined. The external magnetic flux passes through the magnetic-abrasive powder and the metal part, magnetizes them, and therefore the part magnetically attracts the magnetic-abrasive powder. Simultaneously, a gradient of the magnetic field is produced which retains the magnetic-abrasive powder in the working gaps when the part is rotated and not rotated. The gaps are limited by the surface of the pole shoes. It is advisable to further improve the existing magnetic-abrasive machining methods and devices which provide accuracy of machining of the parts and at the same time to increase the material removal rate of machining.
Accuracy of cylindrical parts is characterized by out-of-roundness and deviation of shape of a longitudinal section. With the existing methods of the magnetic-abrasive machining the required out-of-roundness is provided, as disclosed for example in "Machining Time Estimation for Magnetic Abrasive Processes," G. Z. Kremen, et al., Int. J. Prod. Res., 1994, volume 32, number 12, pages 2817-2825. As for the shape of the longitudinal section of a part, it does not correspond to the requirements since the part obtains a barrel-like shape as a result of the machining. The formation of the barrel-like shape is caused by a non-uniformity of the magnetic field both at the pole shoes and in the longitudinal section of the cylindrical part. A gradient of magnetic field is formed along the perimeter of the pole shoes and at the ends of the part. A different value of the magnetic induction leads to a non-uniform pressing of the magnetic-abrasive powder against the part and correspondingly to a non-uniform material removal at the ends of the part.
Another disadvantage is a relatively low material removal rate which is lower than the material removal rate during conventional grinding. The reason for this disadvantage is that the conventional devices for magnetic-abrasive machining cannot generate a value of the magnetic induction more than 1.6 T. This disadvantage is even more substantial when a non-magnetic part composed for example of ceramics, glass, non-ferrous metals, etc. is machined, since the part does not form its own magnetic field and the magnetic-abrasive powder is not pressed against the part.